How does a tiny zipper slider bring two rows of teeth together?
小小的拉链头，怎么让两排齿合起来？
衣服两边的拉链，轻轻一拉，就能合起来。
The zipper along the two edges of a garment can close with a gentle pull.
这么小的拉链头，是怎么做到的？
How does such a small zipper slider do that?
拉链两边有一排排小齿，它们不是真的牙齿。
There are rows of small teeth on both sides of a zipper; they are not actual teeth.
这些小齿长在布带上，能和另一边的齿扣在一起。
These small teeth are attached to fabric tapes and can interlock with the teeth on the other side.
拉链头就是用手拉着走的那个小部件。
The slider is the small part you move by pulling it with your hand.
它里面有一条像字母Y的通道。
Inside it is a channel shaped like the letter Y.
这里的通道，就像能让小齿经过的小路。
This channel is like small paths through which the zipper teeth can pass.
合上拉链时，两边的齿从两条分开的路进入。
When the zipper closes, the teeth on the two sides enter along two separate paths.
它们经过拉链头，在里面靠近，最后扣在一起。
As they pass through the slider, they come closer together inside and finally interlock.
拉链头继续往前走，两排齿就一段段地合起来。
As the slider keeps moving forward, the two rows of teeth close section by section.
反过来拉，通道又把合着的齿分到两条路上。
Pulling in the opposite direction makes the channel separate the interlocked teeth into two paths.
两排齿分开，衣服的两边也就打开了。
When the two rows of teeth separate, the two edges of the garment open too.
所以，拉链不是靠胶水把两边粘住的。
So a zipper does not hold the two sides together with glue.
小齿扣住两边，拉链头则让它们合上或分开。
The small teeth hold the two sides together, while the slider makes them interlock or separate.
